1. Field of the Invention
The present invention relates to a terminal-provided wire including an insulated wire and a metal terminal provided on an end part of the insulated wire.
2. Description of the Related Art
In recent years, a terminal-provided wire including an insulated wire and a metal terminal provided on an end part of the insulated wire has been required to have higher waterproof performance in a wiring harness mounted in an automotive vehicle. The terminal-provided wire having a waterproof function includes a waterproof resin portion covering a waterproof area of an end part. A terminal-provided wire provided with a waterproof resin portion is referred to as a waterproof terminal-provided wire below.
The waterproof resin portion is a part made of synthetic resin and configured to cover a protection area. The waterproof resin portion is formed by insert molding with the protection area including an area from an insulation coating part at the end part of the insulated wire to a connected part of the metal terminal to a core as an insert part.
Further, in a manufacturing process of the waterproof terminal-provided wire, an adhesive is applied to a surface of the insulation coating at the end part of the insulated wire over the entire circumference before the insert molding of the waterproof resin portion. This adhesive becomes an adhesive layer for bonding the insulation coating and the waterproof resin portion to close a clearance between the insulation coating and the waterproof resin portion. This adhesive layer also functions as a water sealing portion for preventing the intrusion of water.
In the waterproof terminal-provided wire, a thermal expansion coefficient of the insulation coating and that of the waterproof resin portion differ. Thus, the adhesive layer needs to have stretchability to be able to cope with a difference in thermal expansion coefficient between the insulation coating and the waterproof resin portion. Generally, silicon-based resin or rubber-based resin having water resistance and stretchability is used as the material of the adhesive that functions as a water sealant.
However, if an adhesive layer of silicon-based resin or rubber-based resin is adopted when an insulated wire includes an insulation coating made of olefin-based resin, adhesiveness (water sealability) between an insulation coating and a waterproof resin portion is insufficient. Thus, water is likely to intrude into a connected part between a core and a metal terminal. This water intrusion causes corrosion and a contact failure in the connected part between the core and the metal terminal.
On the other hand, it is disclosed in Japanese Unexamined Patent Publication No. 2006-123458 to increase adhesiveness between an insulation coating made of olefin-based resin and an adhesive by applying a corona discharge processing or plasma discharge processing to an insulation coating of an insulated wire in the manufacturing process of a waterproof terminal-provided wire.
However, the known approach leads to an increase in the number of manufacturing steps and necessitates the introduction of a costly facility to perform the corona discharge processing or plastic discharge processing in the manufacturing process of the waterproof terminal-provided wire.
The present invention aims to increase water sealability between an insulation coating made of olefin-based resin and a waterproof resin portion without requiring an increase in the number of manufacturing steps and facility in a terminal-provided wire including a waterproof resin portion for covering a connected part of an insulated wire and a metal terminal.